This invention relates to a method for drawing a pattern by deflecting a charged beam within a chip pattern drawing field in major and minor deflection modes, and its apparatus.
To increase the throughput of charged beam drawing, there is known a method in which drawing is performed on a wafer put on a table while the table is continuously moving. In this case, it is necessary to perform correction of the deflection position in accordance with the movement of the table. The term "deflection position" will be used to mean a position of a chip area hit by the deflected beam. This correction is performed during drawing by the minor deflector, by supplying the real position data of the table to the major deflection coil via the table error DAC (digital/analog converter). The system based on the above method is disclosed, for example, in "An electron beam lithography system for submicron VHSIC device fabrication" in J. Vac. Sci. Technol. B3(1), Jan./Feb., 1985, pp. 106 to 111, by H. J. King, et al.
Now, the moving speed of the table is set to a fixed value inherent to a given frame, regardless of the density of the pattern being drawn. Therefore, for example, in a case where the pattern of one sub-field is dense and takes a long time to draw, an amount of movement of the table increases, and an amount of correction of the major deflection position increases accordingly. In accordance with this, it becomes necessary to re-adjust the initially set deflection distortion correction. However, this adjustment of the deflection distortion correction cannot be done until the drawing of the subfield by the minor deflector is finished. For this reason, when an amount of correction of the major deflection position due to the table movement is large, reduction of the accuracy of drawing in the sub-field is problematic because the deflection distortion correction cannot be adjusted. Especially for submicron order pattern drawing, serious problems such as reduction of the production yield due to the deterioration of the accuracy of drawing position arise.